1. Field of the Invention
The present invention relates to a time base error signal generating apparatus for use in an image reproducing apparatus, such as a video disk player or a VCR.
2. Description of Background Information
An image reproducing apparatus, such as a video disk player or a VCR, is so designed as to insert a vertical sync signal and a horizontal sync signal, for example, as sync signals in a video signal, extract both the sync signals from the video signal, and synchronize the sync signals with a reference sync signal to thereby perform coarse and fine adjustments of the time base to read and reproduce video information from a recording medium. Such a sync reproduction requires detection of a time base error of the reproduced video signal with respect to the reference sync signal. FIG. 1 exemplifies a conventional apparatus for detecting this time base error and generating a time base error signal according to the detected error.
Referring to FIG. 1, a phase detector 101 detects the phase difference between a playback vertical reference sync signal Pb-V extracted from a reproduced video signal and a reference vertical sync signal Ref-V, and a phase detector 102 detects the phase difference between a playback horizontal sync signal Pb-H obtained from the reproduced video signal and a reference horizontal sync signal Ref-H. Phase error signals from these phase detectors 101 and 102 are respectively multiplied by appropriate coefficients k.sub.1 and k.sub.2. The multiplied signals are added by an adder 103, and the resultant signal is derived as a time base error signal. According to the thus designed conventional apparatus, an error component generated from the vertical sync signal whose detection accuracy is coarser than that of the horizontal sync signal is dominant, and the phase offset of the vertical sync signal or lower accuracy in detecting the phase difference will influence the accuracy in synchronization. This will disturb the synchronization which is executed at higher accuracy based on the horizontal sync signal. To overcome this shortcoming, the offset between the phase detectors should be adjusted, so that the circuit structure will become complicated.